Apparatus for detecting fluorescence of a luminescent material

Abstract

An apparatus for detecting the fluorescence of a luminescent material. Photo-semiconductors receiving the visible fluorescence from a target luminescent material and directly from a discharge lamp are electrically coupled to oppose each other resulting in a single-channel detector inherently balanced and insensitive to variations in the excitation stimulus. The photo-semiconductor output is sent through a second harmonic amplifier making available a phase detection of the fluorescence instead of an amplitude detection. The phase of the signal is compared with a known phase from the excitation power source. By adding signals that either reinforce or oppose, the phase information is converted back to amplitude information at a voltage level that can be easily detected. The compared output then triggers an indicator producing an indication of the amount of fluorescence of the target luminescent material.

What is claimed is: 
     
       1. An apparatus for detecting the fluorescence of a target luminescent material being excitable at an excitation wavelength and fluorescing at a fluorescing wavelength, comprising: a discharge lamp adapted to be coupled to an alternating current voltage source operating at a source frequency and arranged to excite said target luminescent material at approximately said excitation wavelength;   first response means arranged to be responsive to said target luminescent material at approximately said fluorescing wavelength for providing a first electrical response as a function of the electromagnetic energy received from said target luminescent material at said fluorescing wavelength;   second response means arranged to be responsive to said discharge lamp for providing a second electrical response as a function of the electromagnetic energy received from said discharge lamp;   said first response means and said second response means being arranged such that said first electrical response opposes said second electrical response creating a combined output signal;   a band pass filter coupled to said combined output signal selected to pass predominantly signals of a frequency of approximately twice said source frequency to produce a filtered output signal;   a phase detector coupled to said band pass filter to detect the phase of said filtered output signal and producing a first response when said filtered output signal is of a first phase and producing a second response when said filtered signal is of a second phase; and   an indicator coupled to said phase detector to indicate the condition of said fluorescence of said target luminescent material as a function of at least one of said first response and second response.   
     
     
       2. An apparatus for detecting fluorescence as in claim 1 wherein said first response means and said second response means comprise first and second photo-semiconductors operating in photo voltaic mode, said first and second photo-semiconductors being oppositely coupled in parallel. 
     
     
       3. An apparatus for detecting fluorescence as in claim 1 wherein said phase detector comprises: a rectifier adapted to be coupled to said alternating current voltage source producing a rectified output;   summing means coupled to said band pass filter and to said rectifier for summing said filtered output signal and said rectified output and producing a summed signal wherein a relative high magnitude for the amplitude of said summed signal is indicative of said first response and a relative low magnitude for the amplitude of said summed signal is indicative of said second response.   
     
     
       4. An apparatus for detecting fluorescence as in claim 3 wherein said phase detector further comprises an alternating current voltage source comparator coupled between said summing mean and said indicator which compares the magnitude of the amplitude of said summed signal to the magnitude of the voltage amplitude of said alternating current voltage source and produces said first response as a function of the magnitude of amplitude of said line voltage. 
     
     
       5. An apparatus for detecting fluorescence as in claim 3 wherein said apparatus detects said fluorescence of said target luminescent material above a predetermined threshold and which further comprises an adjustment means coupled to said target luminescent material, to said first or second photo-semiconductors or to said discharge lamp for balancing the output of said first and second photo-semiconductors when said apparatus is measuring a target luminescent material which fluoresces at said predetermined threshold. 
     
     
       6. An apparatus for detecting fluorescence as in claim 5 which further comprises a phase delay coupled between said band pass amplifier and said phase detector to adjust the phase of said filtered output signal to maximize the opposition of the phase of said photo-semiconductor output signal and said rectified signal when said apparatus is measuring a target luminescent material which fluoresces at said predetermined threshold. 
     
     
       7. An apparatus for detecting the fluorescence of a target luminescent material being excitable at an excitation wavelength and fluorescing at a fluorescing wavelength comprising: a discharge lamp adapted to be coupled to an alternating current voltage source operating at a source frequency and arranged to excite said target luminescent material at approximately said excitation wavelength;   first response means arranged to be responsive to said target luminescent material at approximately said fluorescing wavelength for providing a first electrical response as a function of the electromagnetic energy received from said target luminescent material at said fluorescing wavelength;   second response means arranged to be responsive to said discharge lamp for providing a second electrical response as a function of the electromagnetic energy received from said discharge lamp;   said first response means and said second response means being arranged such that said first electrical response opposes said second electrical response creating a combined output signal;   phase conversion means coupled to said first and second response means for converting amplitude variations of said combined output signal to phase variations producing a phase output signal;   a phase detector coupled to said phase output signal to detect the phase of said filtered output signal and producing a first response when said filtered output signal is of a first phase and producing a second response when said filtered signal is of a second phase; and   an indicator coupled to said phase detector to indicate the condition of said fluorescence of said target luminescent material as a function of at least one of said first response and second response.   
     
     
       8. An apparatus for detecting fluorescence as in claim 7 wherein said first response means and said second response means comprise first and second photo-semiconductors operating in photo voltaic mode, said first and second photo-semiconductors being oppositely coupled in parallel. 
     
     
       9. An apparatus for detecting fluorescence as in claim 7 wherein said phase detector comprises: a rectifier adapted to be coupled to said alternating current voltage source producing a rectified output;   summing means coupled to said phase converter and to said rectifier for summing said filtered output signal and said rectified output and producing a summed signal wherein a relative high magnitude for the amplitude of said summed signal is indicative of said first response and a relative low magnitude for the amplitude of said summed signal is indicative of said second response.   
     
     
       10. An apparatus for detecting fluorescence as in claim 9 wherein said phase detector further comprises an alternating current voltage source comparator coupled between said summing means and said indicator which compares the magnitude of the amplitude of said summed signal to the magnitude of the voltage amplitude of said alternating current voltage source and produces said first response as a function of the magnitude of amplitude of said line voltage. 
     
     
       11. An apparatus for detecting fluorescence as in claim 7 wherein said apparatus detects said fluorescence of said target luminescent material above a predetermined threshold and which further comprises an adjustment means coupled to said first or second photo-semiconductor or to said discharge lamp for balancing the output of said first and second photo-semiconductors when said apparatus is measuring a target luminescent material which fluoresces at said predetermined threshold. 
     
     
       12. An apparatus for detecting the fluorescence of a target luminescent material being excitable at an excitation wavelength and fluorescing at a fluorescing wavelength comprising: a discharge lamp adapted to be coupled to an alternating current voltage source arranged to excite said target luminescent material at approximately said excitation wavelength;   first response means arranged to be responsive to said target luminescent material at approximately said fluorescing wavelength for providing a first electrical response as a function of the electromagnetic energy received from said target luminescent material at said fluorescing wavelength;   second response means arranged to be responsive to said discharge lamp for providing a second electrical response as a function of the electromagnetic energy received from said discharge lamp;   said first response means and said second response means being arranged such that said first electrical response directly offsets said second electrical response creating a combined output signal;   an indicator coupled to said first response means and to second response means and responsive to said combined output signal to indicate the fluorescence of said target luminescent material based upon said combined output signal.   
     
     
       13. An apparatus for detecting fluorescence as in claim 12 wherein said first response means and said second response means comprise first and second photo-semiconductors operating in photo voltaic mode, said first and second photo-semiconductors being oppositely coupled in parallel. 
     
     
       14. An apparatus for detecting fluorescence as in claim 12 wherein said apparatus detects said fluorescence of said target luminescent material above a predetermined threshold and which further comprises an adjustment means coupled to said first or second photo-semiconductors or to said discharge lamp for balancing the output of said first and second response means when said apparatus is measuring a target luminescent material which fluoresces at said predetermined threshold.